I have one.
It amazes me when you take flying lessons they make you buy a slide rule. I took engineering in the early 80's and we had programable caluclators then. Slide rules were something the guys in the early 70's used.
But in flying you still have to buy one. Having said that they are kind of cool for converting liters to gallons to US gallons and for converting Knots to MPH to KPH.